This part of IEC61069 : specifies the detailed method of the assessment of operability of basic control system (BCS), based on the basic concepts of IEC61069‑1 and methodology of IEC61069‑2 ; defines basic categorization of operability properties; describes the factors that influence operability and which need to be taken into account when evaluating operability; provides guidance in selecting techniques from a set of options (with references) for evaluating the operability.